Construction arrangement



y 1964 R. w. KRAFT 3,139,959

CONSTRUCTION ARRANGEMENT Filed June 12, 1961 FIGJ 2 Sheets-Sheet l Maw m, 3 3$! 72 74 INVENTOR RALPH w- KRAFT p/sm/arzo cue/c W BY ATTORNEY y 7, 1964 R. w. KRAFT 3,139,959

CONSTRUCTION ARRANGEMENT Filed June 12, 1961 2 Sheets-Sheet 2 F'|G-2 F163 FIG-4 INVENTOR United States Patent 3,139,959 CONSTRUCTION ARRANGEMENT Ralph W. Kraft, Glastonbury, Conn., assignor to United Aircraft Corporation, East Hartford, Conn., a corporation of Delaware Filed June 12, 1961, Ser. No. 116,543 2 Claims. (Cl. 189--34) This invention relates to construction arrangements and more particularly to those truss-like bracing arrangements which are designed to be as rigid as possible and at the same time lightweight.

It is a primary object of this invention to provide an extremely rigid, relatively low-density construction arrangement having symmetrical properties and of great versatility.

It is a further object of this invention to provide a construction arrangement of the type described comprising an arrangement of rods in the form of the carbon-carbon bonds in a diamond crystal which can be assembled into an array of any size (larger than the unit cell) in three dimensions. The assembly is then covered by suitable skin surfaces or tie rods or equivalent around the periphery of the assembly to provide a rigid, very lightweight construction arrangement.

It is a further object of the present invention to provide a modified construction arrangement of rods in the form of the lines adjoining the lattice points of a distorted diamond cubic lattice which can be assembled into an array having special properties. In one modification of this variation, for example, two cylindrical skin surfaces are braced, one to the other, by means of the skeletal structure based upon a cylindrically distorted diamond cubic lattice.

Rigid structures are required in a variety of applications embracing the missile and space field, as well as civil structures. Conventional forms of such structures having high strength and low weight include built-up trusses and honeycomb and sandwich construction with foamed materials, etc., where each element of the structure is stressed to the same degree insofar as is possible so that maximum efiiciency is obtained.

The unique construction arrangement described herein which has the properties of rigidity, high strength, and low weight is described hereinafter in connection with the drawings in which:

FIG. 1 is a representation of a cubic unit cell upon which the simplest structural arrangement is based. Hereinafter, this is called the cubic modification;

FIGS. 2, 3, and 4 are side and end views of a typical unit rod capable of use in the cubic modification;

FIG. 5 is a subassembly of rods of the type shown in FIGS. 2, 3, and 4;

FIG. 6 is aperspectiv'e of a model showing the skeletal arrangement of rods comprising those in one typical unit cell, cubic modification;

FIG. 7 is a perspective view illustrating the way the skeletal arrangement of adjoining typical unit cells of the cubic modification fittogether; and

FIG. 8 is a schematic diagram showing another unit cell arrangement which could be used as a basis for developing an analogous skeletal structural arrangement having features similar to the simpler cubic modification.

FIG. 1 is a projection of a portion of what might be termed an infinite array of points in three-dimensional 3,139,959 Patented July 7, 1964 space. The points in space are not arranged randomly but in a special periodic sequence in three dimensions; the projection is made so as to clarify the description of the periodic array of points in space. The repetitive unit of points, in three dimensions, can most easily be described in crystallographic terms as the diamond cubic arrangement of points in space.

The unit cell of the diamond cubic arrangement of points in space is a cube, with sides equal and mutually perpendicular and points at each corner of the cube, in the center of each face and others displaced from these by A1 of a unit translation in each of the three mutually perpendicular crystallographic directions. In the language of the crystallographer the diamond cubic arrangement of points in space is completely specified by stating:

(a) That the cell is cubic, and (b) That there are points at (1) 0, 0, 0-the cell corners (2) /2, /2, 0; /2, 0, /2; O, /2, /2-centers of cell faces (3) A, /4, A; /1, A, /4; A, A,

diamond cubic translations This definition explicitly implies that the arrangement is infinitely repetitious. For example, consider one corner of one cube and arbitrarily assume that the three crystallographic directions or vectors are the three lines (cube edges) meeting at this corner. The above definition (b) (1) describes the specific corner in question; the other seven corners of the cube can be derived from this by unit translations of the three crystallographic vectors (0, O, 1; O, 1, 0; 1, 0, 0;1,1, 0;1, O, 1; 0, l, 1; l, 1, 1). Other corners of other adjacent cubes are obtained by additional unit translations which can be in either a positive or negative direction with respect to any or all axes. In the same way the unit cell of the diamond cubic arrangement of points in space is understood to be the basic unit from which an infinite array of points could be obtained by integral multiples of unit translations from the eight points described above in one unit cell at the origin.

The cubic modification of the construction arrangement described herein is an arrangement of rods connecting points which are nearest neighbors in the diamond cubic arrangement of points in space. It is called the diamond cubic arrangement because in this (cubic) modification of the present invention, the rods represent or are analogous to the carbon-carbon bonds in a diamond crys tal. It will be noted in FIG. 1 that four such rods meet at every point, and that an identical configuration (except for inversions) exists at each point. The four rods meeting at each point, in fact, are normal to the faces of a regular tetrahedron centered on the point.

The angles that the rods of this invention assume in their assembled state are computed by a crystallographic formula to be 109.47 (FIG. 5). This is based on the fact that the rods are arranged like the carbon-carbon bonds in a diamond crystal. Thus, if desired, the rods can be formed as single elements 10 as shown in FIGS. 2, 3, and 4 which include beveled surface portions 12, 14, and 16. The beveled surfaces form an angle of approximately 54.74 with the axis of the rod. These individual rods can be suitably connected as by synthetic bonding, brazing, or welding to three other rods at each end in the preferred arrangement. The rods can be suitably "a as fastened together to form skeleton structures which can be stacked in three dimensions to whatever suitable shape the final product is to assume.

Alternate methods of constructing a skeletal assembly of rods of the cubic modification can be devised because of the high symmetry and essential simplicity of the construction arrangement. One such alternate method is illustrated by FIG. 5. This is a sketch of a multiple unit piece consisting of more than two (and as many as desired) units formed as a unit in the manner shown. These multiple unit pieces (zigzags or Ws) when placed alternately perpendicular to each other in parallel groupings of the proper spacing (which is determined by the pieces themselves) will form a three-dimensional network of the type described previously. Other methods (viz., four-pronged subassemblies, sheet-like subassemblies, and so forth) could also be devised without detracting from the essential construction arrangement described herein.

Thus, it may be desirable to form W-shaped or zigzag elements generally indicated at in FIG. 5. The term W is referred to here for convenience only. It is to be understood that the zigzag or W shape can be continuous and not limited to four legs. Those rods in one unit cell (cubic modification) of such an assembly are shown in FIG. 6. The assembly of rods comprising two adjacent unit cells are shown in FIG. 7, but it should be realized that as many cells of the type shown in FIG. 6 can be placed adjacent to one another and that the cells can be built next to one another in three dimensions. FIG. 7 is only intended to illustrate the fact that two cells will fit together in the same manner that two solid cubes will fit together side by side to fill space. Obviously, many cubes can be placed together face to face to fill space in three dimensions. In the same way the skeletal structural arrangement can be built up continuously in all three dimensions as so desired depending upon the application. Thus, it can be seen that a basic W-shaped or zigzag element 22, as illustrated in FIGS. 6 and 7, may comprise four (or more or less) legs 24, 26, 28, and 30.

If single elements are to be connected, they may comprise single rods such as 32, 34, 36, and 38 connected at a common joint 40, this forming a four-pronged subassembly. In any event, these individual assembled elements such as 22 or a group commonly connected, as for example at the joint 40, can be prefabricated and grouped together with other similar units to stack the elements. It may further be desirable to form the units in individual cells such that, as shown in FIG. 7, the entire halfassembly to the right of the dotted line 50 would form one cubic unit while the half-assembly to the left of the line 50 represents a second individual cubic unit; or else a four-pronged subassembly as mentioned above may be provided with a rod joint at the center. These units of cubic structure can then be assembled in all three dimensions and enlarged to form a suitable structural entity. On the other hand, the individual unit elements can be used in an enlarged three dimensional arrangement of any size.

It should be pointed out that the angles between adjacent rods are all equal with respect to the point of junction. Thus, at any junction the rods meet at equal angles with respect to each other, regardless of which pair of rods is compared.

If desired, as shown in FIG. 7, a given number of units may be assembled and surface sheets 60 and 62 may be suitably bonded or connected thereto for the proper finishing steps. The sheets may be merely web connectors or can be imperforate or perforated to any desired extent as long as the strength requirements are met. It should be noted, however, that the showing of one cube height in FIG. 7 is for purposes of illustration only and that the height or other dimensions may be enlarged to a plurality of cube dimensions as may be necessary.

As a result of this invention it will be apparent that a very lightweight structure has been provided which provides a number of advantages.

Each end of each rod is held rigidly in place in three dimensions by three other pieces making equal angles with the supported piece and with each other. Thus, a rigid skeletal structure is obtained when the diamond cubic bracing is appropriately combined with a skin or other surrounding connecting members or other suitable sheathing.

Since the structure is based upon a cubic unit cell, the properties of the structure will have the high symmetry of the cubic system.

Because the structure is composed of rods rather than webs or sheets, the void space is continuous (and regular) throughout the structure. Thus, bulk materials such as insulation, refractory and fluids or wires, pipes, tubes, etc. can be interspersed in any fashion throughout a braced structure.

Because of the essential simplicity of the unit pieces and the high symmetry of the packing arrangement, the structure is amenable to mass production and can be adapted to meet specific requirements. The rods can be of any cross-sectional shape (round, hexagonal, extruded shapes, hollow, or solid) and made of any solid material (metal, glass, ceramic, wood, plastic) by whatever method is suitable (pressing, molding, casting, forging, machining, grinding, sawing, extruding, etc.) and joined by whatever method is feasible (brazing, welding, gluing, specially designed joint blocks, etc.). As previously mentioned, much labor can be saved by the zigzag construction for materials which could be so formed. The size of the unit pieces, their cross-sectional shape, and their L/d ratio can be varied to suit the requirements. Just as long as the length is the same and the ends are properly formed, pieces of different materials, difierent diameter or cross-sectional shape could be built into the same assembly to give a structure with continuously varying properties. Thus, weight could be saved where possible and strength added where necessary.

It should also be added that the essential simplicity and high symmetry of the construction arrangement permit wide flexibility in application, even including extensions of the concept to non-cubic unit cells.

Modifications of the construction arrangement other than the cubic modification can be made. The cubic or diamond cubic modification, of course, has the highest symmetry and is simplest mathematically. However, this invention is not intended to be restricted to only the cubic modification. For example, FIG. 8 illustrates a variable unit cell scheme which might be a preferable arrangement for bracing two concentric cylinders 70, 72. Thus, ele ments or units 74, 76 of varying shape may be utilized. Other non-cubic modifications could also be devised. In any modification, the unit cells, whether of the same size or of continuously varying size (such as shown in FIG. 8 for example), will be such that when packed together they will fill the space desired without gaps. As illustrated for one example in FIG. 8, the diamond cubic type bracing arrangement is then appropriately distorted in the same mathematical manner as the unit cell was distorted from a cube so that an analogous three-dimensional truss-work is produced.

Although several embodiments of this invention have been illustrated and described herein, it will be apparent that various changes may be made in the construction and arrangement of the various parts without departing from the scope of the novel concept.

What it is desired by Letters Patent is:

1. A load bearing construction arrangement comprising a plurality of elongated members of substantially equal length, four of said members being rigidly connected to each other at one of their ends in angular relation and forming a first joint, each of said four members forming substantially an equal angle with each other of said members, and at least one other joint formed at the other end of one of said four members, said joint being formed by at least one other member of substantially the same length as said four members and said members at said other joint forming an angle with each other substantially identical to the angles formed at said first joint, and at least one outer sandwich layer bonded to said members to form a unitary structure.

2. A load bearing construction arrangement comprising a plurality of elongated members of substantially equal length, four of said members being rigidly connected to each other at one of their ends in angular relation and forming a first joint, each of said four members forming a substantially equal angle with each other of said members, and at least one other joint comprising a second four members of the same length as the members of each first joint, and forming angles with each other substantially identical to that formed by the members of said first joint, one member being common to both joints and forming a rigid connection therebetween, and an outer skin layer bonded to said members to form a unitary structure.

References Cited in the file of this patent UNITED STATES PATENTS 2,356,675 Lachman Aug. 26, 1944 2,869,693 Wood Jan. 20, 1959 2,967,594 Deam Jan. 10, 1961 2,979,169 Yolles Apr. 11, 1961 2,986,241 Fuller May 30, 1961 FOREIGN PATENTS 1,124,180 France Oct. 5, 1956 OTHER REFERENCES Wells, A. F.: Page 431, Structural Inorganic Chemistry, Oxford University Press, 1945. 

1. A LOAD BEARING CONSTRUCTION ARRANGEMENT COMPRISING A PLURALITY OF ELONGATED MEMBERS OF SUBSTANTIALLY EQUAL LENGTH, FOUR OF SAID MEMBERS BEING RIGIDLY CONNECTED TO EACH OTHER AT ONE OF THEIR ENDS IN ANGULAR RELATION AND FORMING A FIRST JOINT, EACH OF SAID FOUR MEMBERS FORMING SUBSTANTIALLY AN EQUAL ANGLE WITH EACH OTHER OF SAID MEMBERS, AND AT LEAST ONE OTHER JOINT FORMED AT THE OTHER END OF ONE OF SAID FOUR MEMBERS, SAID JOINT BEING FORMED BY AT LEAST ONE OTHER MEMBER OF SUBSTANTIALLY THE SAME LENGTH AS SAID FOUR MEMBERS AND SAID MEMBERS AT SAID OTHER JOINT FORMING AN ANGLE WITH EACH OTHER SUBSTANTIALLY IDENTICAL TO THE ANGLES FORMED AT SAID FIRST JOINT, AND AT LEAST ONE OUTER SANDWICH LAYER BONDED TO SAID MEMBERS TO FORM A UNITARY STRUCTURE. 